River network connectivity and fish diversity.

Frequent and severe disruptions of natural river flows associated with human activities significantly alter hydrological connectivity in large river networks, with deleterious effects on fish diversity. Understanding the relationship between fish diversity and river network connectivity is fundamental to ensuring species persistence, ecosystem integrity, and human well-being. Here, we provide a review of the mechanisms by which river network connectivity (RNC) affects fish diversity. We review the relationships between forms, systems and types of RNC and fish diversity, based on more than 100 previous studies. In summary, sustaining RNC promotes fish diversity in longitudinal and lateral axes, and species sorting, dispersal dynamics, and habitat availability are the main factors driving the distribution of fish diversity, followed by nutrition and trophic dynamics. Our work highlights the effects of RNC on fish diversity, and provides a mechanistic understanding of how RNC affects fish diversity across river basins, thus providing scientific guidance for protecting fish biodiversity and improving the health of river network ecosystems.